Title: Design Evaluation of Multiroll Mills for Small-diameter wire rolling
1Design Evaluation of Multiroll Mills for
Small-diameter wire rolling
- Paper by K. Kuroda, T. Kuboki, Y. Imamura
Presentation by Adam Slade Monday, 17 September,
2007
2Background
- Wire rolling is being utilized rather than the
more traditional wire drawing method of
production. A round rod is used as a starting
place for the ensuing rolling reductions.
3Purpose of the Paper
- Demonstrate differences in forces and
advantages/disadvantages of wire rolling using
different numbers of rollers - Show wire rolling to be a good alternative to
wire drawing, specifically wire rolling with
multiple rollers
4Why?
- Conversion from drawing to rolling ensures a
high reduction in area per pass, because the
severe sliding frictional condition is almost
eliminated. - The Reality most of the contact area of the
rollers with the wire involves sliding friction,
and no data is provided as a comparison between
the two methods
5Comparison to Previous Work
- Many papers/studies had been previously been made
examining the advantages and disadvantages of
multiple rolls in wire manufacture - Authors angle none of the previous studies
has compared the deformation and loading
characteristics of the three mills on an even
basis, i.e. on the same roll and groove geometry
design basis, and direct one-to-one comparisons
have not been made of all three mills on a
numerical and experimental basis.
6Authors Possible Motive
- Such study may enable further development of the
multiroll cold wire rolling mill in the next
decade. - The authors created a four-roll micromill named
the super-micromill
7Objectives in Design
- There was to be no tension in the wire between
stands (as opposed to the drawing method) - Driving torque given from one source to all
stands through a common drive (one motor) - Compact design
8Limitations of Experimentation
- Only to examine 2, 3 and 4 roll stands
- Stand composed of more than five rolls is not
realistic because of complexity - Why a 5 roll stand is not examined
9The Setup
- 2 roll unit driven by two shafts
- 3 and 4 roll unit driven by single shaft
- Roll force measured using load cell
- Driving torque calculated by revolution rate and
power consumption
10(No Transcript)
11Specifications for prototype mill
Authors offer no explanation for calculation of
nominal roll diameter, or rolling speed
12Obtaining Results
- Contact Area with rollers
13Comparing the Model to the Data
- Conclusion Why bother with any further actual
experimentation?
14Considerations for further models
- Mother wire to come from smallest available
hot-rolled rod on the market - 5 or 6 mm
- Minimum diameter wire taken as the smallest wire
in the world - The authors report it to be 1.2 mm
- Minimum diameter produced from first source
investigated found to be 0.14 mm for Cu, 0.25 mm
for aluminum, 0.38 mm for carbon steel - Reference obtained from the authors own previous
paper - Roll diameter comes from accepted market data
- Minimum ratio of roll diameter to wire diameter
is 20 - Maximum roll size based on the following
statement
- It is known that, the larger the roll shaft and
the machine size, the larger is the bearing load
but the higher the machine cost.
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16Finite Element Analysis
- CORMILL finite element code developed by the
University of Tokyo - For three-dimensional rigid-plastic steady
state analysis of rolling - Performed over one-half of the contact area with
each roller
17Results
- As the reduction in area increases, ovality
increases - This tendency becomes greater as the ratio of
roll diameter to wire diameter increases
18Manipulation of Results
- Over-emphasis on ovality favors the 4-roll
configuration. Ovality the only consideration in
precision. - the four-roll mill is most advantageous in
ensuring precision when subjected to
smaller-diameter wire rolling.
19Comparison of Results
- It has been said that, the smaller the number of
rolls, the higher the reduction becomes, i.e.
better performance can be obtained in the order
two-rollgtthree-rollgtfour-roll. but - This paper compares the performance given equal
dimensional tolerances, on unequal measuring
techniques.
20Loading Results
- the two-roll mill requires greater torque than
either the three- or four-roll mills. - Total rolling force is equivalent for all
rollers, indicating the same power requirement
for each configuration
21Torque inequalities
- The three different configurations require
different torque requirements. Not an even
comparison. - Assumption of constant frictional work on each
roller likely false, due to different contact
areas/deformations.
22Force vs. Torque
- Rolling force is approximately equal
- Power requirement based on force, not torque
- Lower portion shows the inequalities in the setup
of equipment
23Calculations based on
- Three data points enough?
24More Unfair Comparisons
- Measuring rolling force per one roll
- Not linear as shown
- Isnt it obvious that the rolling force per roll
should decrease this drastically for an increased
number of total rolls? - Red lines indicate the 2- and 3-roll positions
normalized (as if all rollers had four members) - the three-roll actually has the lowest total
rolling force
25Conclusion Disadvantages and Considerations
- Prolonged manufacture time, due to greater
restrictions on reduction ratio - More complex machinery twice as many rollers
twice as much maintenance - Other effects on the final product not considered
(additional work hardening, heat introduced into
machinery due to greater deformations, etc.)
26Conclusion Advantages and Implications
- The four-roll micomill would provide a good way
to create high tolerance small diameter wire for
a lower energy requirement over drawing, and a
very slightly lower energy requirement over a
two-roll mill - This improve the efficiency of the wire industry
greatly, if high tolerances are more desirable
than the increase in equipment and increase in
processing time
27References
- Four of the sources are the authors own work,
all but four are from Japan (presumably written
by coworkers), and those four are from 1983,
1983, 1982, and 1952